Recombinant DNA technology will be used to investigate the genetic and biochemical bases for the pathogenicity of Streptococcus mutans. S. mutans DNA has been and will continue to be cloned into appropriate hosts of Escherichia coli K-12 and Bacillus subtilis 168. Clones specifying genetic information thought to be important in contributing to the ability of S. mutans to colonize and display virulence will be characterized by genetic, biochemical and immunologucal techniques. The specific projects to be pursued are: (i) to determine the mechanism for regulating the S. mutans gene coding for aspartic acid semialdehyde dehydrogenase in E. coli versus S. mutans, (ii) to determine the role of the 210,000 M.W. surface protein antigen A (specified by the spaA gene) in S. mutans virulence and the manner of its interaction with dextranase cleaving Alpha 1 yield 6 linkages, (iii) to determine the functions of the surface protein antigens specified by 20 recombinant cosmid clones that produce proteins that react with antibodies against S. mutans cell surface proteins, (iv) to continue characterization of the glucosyltransferase specified by the S. mutans gtfA gene and the structure of the glucan synthesized, (v) to determine the mechanisms of protein modification and translocation across the cytoplasmic membrane in Gram-positive versus Gram-negative bacterial hosts, and (vi) to clone additional genes specifying glucosyltransferases, fructosyltransferases, invertases, dextranases and glucan-binding proteins which will be characterized for their contributions to S. mutans virulence. The research will be done in conformance with the NIH Guidelines for Recombinant DNA Research. The studies will make use of the technologies of molecular genetics, microbiology, biochemistry and immunology.